Extra annotations

@qidane and @chris-allan: as long as we're cleaning up the whitespace, then we should properly address this file (**and** backport the non-breaking changes to `dev_5_0`). I've done most of that here.

Especial attention should be paid to:
 * c01e8ed
 * 145de75

I may well have misunderstood the indent of some of the TODO comments, but I think we're in a much better place. @qidane, there also remain a small hand-full of TODO markers of the form `OMERO data type mismatch`. If you could at least look at those, I'd appreciate it.

My goal would be to have this file flag free so that further work on it is much clearer for others.

/cc @mtbc